Device For Driving The Folding Arms Of An Interfolding Machine

ABSTRACT

The device for driving folding arms of comb-like folding means along a closed operating path is used on an interfolding machine  100  for production of interfolded packs of sheets of tissue paper or another material and is mounted on a frame  10   a  situated in the lower part of the machine  100 . A connecting rod-crank transmission assembly  13  is mounted on the frame  10   a  and connected to the comb-like  2 , to drive the latter along the closed operating path. The driving device  10  comprises also a main motor  51 , aimed at supplying at least a part of mechanical power necessary to drive the comb-like  2 , and a supplementary motor  55 , running at a controllable rotation speed, aimed at cooperating with the main motor  11 , in driving the comb-like  2 . An epicycloidal type differential  20 , connected mechanically to the main and supplementary motors  51  and  55 , and to the transmission assembly  13  as the combination of the power received at the intakes. A control unit is also provide in the interfolding machine  100  for adjusting the rotation speed induced by the supplementary motor  55  in relation to the position assumed by the folding arms  3  in the above-mentioned operating path.

BACKGROUND OF THE INVENTION

The present invention relates to the technical field concerning automatic machines for manufacturing and packaging of disposable articles of tissue paper or another similar absorbing material, into interfolded packs.

In particular, the invention concerns a device for moving folding arms in an interfolding machine, aimed at obtaining such interfolded packs of disposable articles, beginning from continuous strips of the material being used.

BRIEF DESCRIPTION OF PRIOR ART

It is known that different types of disposable paper articles, such as handkerchiefs, napkins, towels, toilet paper, etc. are often sold in the form of sheets, packaged in packs made of a certain number of folded sheets, stacked one over another and interfolded. This means that each sheet is folded by the aforesaid machine so as to obtain two or more folding flaps, and then it is stacked so that the flaps of adjacent sheets of the stack are co-penetrating. For example, in the case of three flaps folding, the first flap of a sheet is contained in the folding of the previous sheet and, the first flap of the subsequent sheet is in turn contained between the second and third flaps. In this way, during the use, by removing a sheet from the pack of articles, also the first flap of the subsequent sheet is freed. This facilitates the subsequent withdrawing of the latter.

The conventional, most common interfolding machines include a plurality of rollers material from which the articles are obtained. dimensions sheet direction roller partially overlays the sheet

At the outlet of the folding rollers, the partially overlaid sheets are taken by a pair of comb-like oscillating devices, provided with a plurality of folding arms, parallel to one another, that separate the overlaid portions of two subsequent sheets from each roller and form the interfolded stack. The folding arms move along a close trajectory that includes a first extreme position, in which the arms are introduced into suitable grooves made in the folding rollers, and a second extreme position, in which the arms protrude outwards of the aforesaid rollers, taking with them a flap of the forthcoming sheet to put it on the stack being formed.

The known comb-like devices are hinged on axes parallel to the folding rollers and are generally moved in step relation with the sheets forward movement on the rollers, by means of a mechanism equipped with connecting rod-crank assemblies operated by cam guides. The driving action derives from the interfolding machine main drive, by means of known mechanical transmission devices.

A suitably studied cam profile allows the folding arms to execute their movements with required timing and to increase, reduce or even set to zero their movement speed, depending on the position occupied in the close trajectory.

A disadvantage of the conventional driving mechanisms of the above mentioned comb-like devices derives from the fact that the inertia of these mechanisms components, in particular of the cams and connecting rod-crank assemblies imposes quite serious limits to the folding arms working speeds.

OBJECTS OF THE INVENTION

Another important drawback of the known driving mechanisms derives from the fact that it is necessary to change the cam group each time it is requested to change the trajectory of the folding arms, or the timing in which such trajectory is followed.

It is an object of the present invention to propose a device for driving the folding arms in an interfolding machine, which is capable of defining the trajectory thereof in a way substantially independent from the presence of the cam mechanisms, and thus capable of obtaining higher working speeds with respect to those allowed by the conventional driving devices.

Another object of the invention is to propose a driving device capable of allowing immediate variations which can be realized simply by the folding arms trajectories, by the timing, with which the trajectories are followed, and by both characteristics.

A further object of the invention is to propose a driving device that is extremely precise and reliable.

SUMMARY OF THE INVENTION

The above mentioned objects are wholly obtained in accordance with the contents of the claims, by a device for driving the folding arms of comb-like folding means along a closed operation path, used on the interfolding machine for the production of interfolded packs of sheets of tissue paper or another material, mounted on a frame situated in the lower part of the machine.

A connecting rod-crank transmission assembly is mounted on the frame and connected to the above mentioned comb-like, aimed at driving the latter along the closed operating path.

The driving device comprises also a main motor, aimed at supplying at least a part of mechanical power necessary to drive the comb-like, and a supplementary motor, of controlled rotation speed, aimed at cooperating with the main motor in driving the comb-like.

An epicycloidal differential, connected mechanically to the main and supplementary motors and to the transmission assembly, receives at the inlet the rotational mechanical power generated by the main and supplementary motors, respectively, and supplies at the outlet the corresponding rotational mechanical power to the transmission assembly as the combination of the energy received from the inlets.

A control unit is also provided in the interfolding machine for adjusting the rotation speed caused by the supplementary motor depending on the position assumed by the folding arms in the above mentioned operating path.

BRIEF DESCRIPTION OF DRAWINGS

The characteristics of the invention, as they will become apparent from the claims, are pointed out in the following detailed description, with reference to the enclosed tables of drawings, in which:

FIG. 1 is a schematic side view of the main structure of an interfolding machine, equipped with a pair of folding assemblies;

FIG. 2 is a prospective view of one of the folding assemblies of FIG. 1, provided with the folding arms driving device obtained according to a first embodiment of the present invention;

FIG. 3 is a top view of the folding assembly of FIG. 2;

FIG. 4 is a top view of the folding assembly in a second embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

With reference to FIG. 1, the main operating means of a machine 100 for interfolding sheet articles 1, such as, for example, towels made of tissue paper, are illustrated schematically.

The interfolding machine 100 comprises, according to a known technology, a pair of counter-rotating cutting rollers 101 a, 101 b, a corresponding pair of folding rollers 110 a, 110 b, likewise counter-rotating and arranged below the cutting rollers 101 a, 101 b, and corresponding folding assemblies, which comprise a pair of comb-like folding means 2 arranged below the folding rollers 110 a, 110 b.

The comb-like 2 comprises substantially a plurality of folding arms 3 mounted parallel one to another and equidistant on a shaft 4 rotating on its axis (see also FIG. 2). The shaft 4 is mounted parallel to the axis of the corresponding folding roller 110 a, 110 b, so that each folding arm 3 is equidistant from the surface thereof.

The folding arms 3 are aimed at oscillating periodically, in a suitable phase relation with the rotation of the folding rollers 110 a, 110 b, along a closed operating path, which allows them to detach the towels 1 from the same folding rollers 110 a, 110 b, to withdraw them and fold them according to folding schemes, likewise known.

With reference to FIGS. 2 and 3, the folding arms 3 are driven along the above mentioned operating path by a driving device 10, made according to a first embodiment of the present invention.

The driving device 10 comprises a frame 10 a, situated below the corresponding folding roller 110 a, 110 b, which receives, in its front part, the above mentioned folding means 2, putting them in a position parallel with respect to the aforesaid rollers. The device 10 comprises also motor means 50, having electronically controlled speed and whose structure and conformation constitute the basis of the invention.

In the aforesaid first embodiment, the motor means 50 comprise first of all main motor means 51, mounted at an end of the frame 10 a, aimed at supplying at least a part of the mechanical power necessary to move the comb-like 2, as it will become evident from the following part of the description. The main motor means 51 are constituted by a derivation from the interfolding machine 100 general drive, in the drawings schematized simply with a shaft and a pulley, connected to a mechanical transmission assembly 31 by means of a belt 11. It is to be noted that substantially this derivation speed cannot be controlled, at least, in particular, having regard to the driving device 10, and therefore it is to be considered steady.

The transmission assembly 31 includes a phaser-overgear transmission box device 32 of known type, which is connected, by means of a further belt 33 and a pair of pulleys, to an end of a shaft 34 supported by the frame 10 parallel to the shaft 4 of the comb-like 2.

At the opposite end, the shaft 34 is connected, by means of a pulley and a transmission belt 35, to differential adjustment means 20, made of a mechanical epicycloidal differential.

In particular, the transmission belt 35 engages with a first power intake 21 of the aforesaid differential 20, provided in the moving casing thereof.

The differential 20 used, as already mentioned, comprises advantageously a device, commercially available on the market, that includes a first power intake 21 in correspondence to its moveable casing, a second axial power intake 22 and a power take-off 23, likewise axial and aligned with the axis of the second intake 22.

The differential 20 is mounted on transversal supports made in the frame 10 with the axis parallel to the axes of the shaft 4 of the comb-like 2 and of the shaft 34 of the transmission assembly 31.

The output of supplementary motor means 55 is connected axially with the second power intake 22, said supplementary motor means 55 being mounted on one of the transversal supports of the frame 10 and aimed at cooperating with the above mentioned main motor means 51 to drive the comb-like 2. In particular, the supplementary motor means 55 comprise advantageously a brushless type motor, whose angular position, and consequently, whose instantaneous velocity in both directions can be controlled with extreme accuracy, and therefore allow to define its instantaneous velocity and position by means of a programmable control unit. In any case, the aforesaid type of motor is not to be considered limiting or exhaustive. An excellent electronic control of the rotation speed can be obtained also with other types of electric motor, for example with an asynchronous motor or a stepping motor.

Ultimately, the differential 20 is aimed, according to the invention, at receiving at the intake the rotational mechanical power from the main motor 51 and from the supplementary brushless motor 55, and at supplying at the output the rotational mechanical power with the rotation speed defined by the combination of the rotation speed imposed by the main motor 51 on the first power intake 21 and on the second power intake 22.

An output transmission shaft 14, connected axially to the take-off 23 of the differential 20, is in turn connected mechanically to mechanical transmission means 13, aimed at driving the comb-like folding means 2.

The mechanical transmission means 13 comprise substantially a connecting rod-crank assembly consisting of a connecting rod 13 a, coupled at one end to a crank 13 b, made in the aforesaid transmission shaft 14, and with the opposite end of the connecting rod 13 a connected eccentrically to the shaft 4 of the comb-like 2. In this way, a complete rotation of the output transmission shaft 14 corresponds to a cycle of oscillation of the folding arms 3, which brings the latter to cover the above mentioned closed operating path, with a known conformation.

According to the operation of the above described driving device, the main motor 51 works, in a substantially conventional way, with constant rotation speed, and defines the basic driving speed of the folding arms 3, by means of the mechanical transmission assembly 31, the casing of the differential 20 and the connecting rod-crank assembly 13.

The rotation speed of the supplementary motor 55, in turn, is defined depending on the position assumed by the folding arms 3 along the closed operating path, by means of a suitable program stored in the control unit of the interfolding machine 100, or in a dedicated control unit of the device 10. The rotation speed induced by the supplementary motor 55 in the second power intake 22 of the differential 20 is then added, at the output on the corresponding power take-off 23, to the rotation speed induced by the main motor 51, if the rotation directions of the two motors are concordant, and subtracted therefrom if the supplementary motor 55 is driven to rotate in the direction opposite with respect to that of the main motor 51.

Consequently, it seems evident that the possibility offered by the brushless supplementary motor 55 to control and define its instantaneous position and velocity point per point, allows to impose to the folding arms 3 any acceleration or deceleration with respect to the basic speed, requested to modify the timings of the folding arms 3 intervention on the sheets 1 to fold.

Such timings can be also advantageously changed simply and immediately, also in the production line, varying only the parameters of the control program of the supplementary motor 55.

A second embodiment of the invention is illustrated in FIG. 4. In such an embodiment the supplementary motor means 55 include a first brushless motor 55 a and a second brushless motor 55 b, mounted symmetrical with respect to the mechanical transmission and conversion assembly 13 with the respective axes being aligned.

The differential transmission means 20, in turn, include a first mechanical differential 20 a and a second mechanical differential 20 b, both of epicycloidal type, mounted respectively opposite to each other on related transversal supports of the frame 10 a and aligned axially with each other and with the aforesaid supplementary motors 55 a, 55 b.

The differentials 20 a, 20 b are provided, respectively, with a first power intake 21 a, 21 b, in correspondence to their respective casing, connected to the main motor 51 by means of a pair of transmission belts 35 a, 35 b, operated together by the mechanical transmission assembly 31, in a way quite similar to what has been already described with reference to the first embodiment of the invention, with a second power intake 22 a, 22 b, connected to the supplementary motors 55 a, 55 b, and with a power take-off 23 a, 23 b arranged in axis with respect to the second power intake 22 a, 22 b.

The power take-offs 23 a, 23 b are in turn connected at the opposite sides to the mechanical transmission and conversion means 13.

The rotation speed of the supplementary motors 55 a, 55 b is defined and made synchronous by a program stored in the control unit of the interfolding machine 100, so that both motors cooperate in identical way to change the speed and acceleration of the folding arms 3 along their closed operating paths.

The advantages related to the use of a double supplementary motor drive as defined in the second embodiment of the invention, derive mainly from the fact that in this way it is possible to use components of smaller dimensions, with limited size increase and obtaining at the same time a substantial cost reduction.

According to another embodiment of the above described invention, that does not change substantially the already illustrated working principles, and that is not illustrated in the figures, since of immediate comprehension, the above mentioned motor means 50 comprise a single motor, aimed only at operating the driving device 10, of the electronically controllable speed type, whose shaft is connected directly to the above mentioned outlet shaft 14. The rotation speed of the motor 50 in this case is controlled directly by the programmable control unit of the interfolding machine 100 or of the device 10.

In this way, the constructive simplicity characteristics of the whole driving system of the device 10 are improved. A drawback of such further embodiment lies in the fact that the motor 50 can present some inertia problems, when the accelerations and decelerations necessary for a full control of the folding arms 3 functionality are to be reached for very high production speeds. The choice to use one embodiment of the invention with respect to other described ones is in any case subjected to suitability evaluation in function of the productivity and performance requirements of the device 10 in each single case.

It is understood that what above has been described as a pure not limiting example. Therefore, possible modifications and variations of the invention are considered within the protective scope of the present technical solution, as described above and claimed below. 

1-11. (canceled)
 12. A device for driving folding arms in an interfolding machine for manufacturing interfolded packs of sheet articles, said interfolding machine (100) comprising: one or more folding rollers (110 a, 110 b), each folding roller receiving in sequence a plurality of sheet articles (1) to be stacked; comb-like folding means (2) having a plurality of folding arms (3), being arranged near each of said one or more folding rollers, each comb-like folding means having a longitudinal axis thereof substantially parallel to an axis of a corresponding one of said one or more folding rollers, said folding arms (3) being movable, in suitable phase relation with the rotation of said one or more folding rollers, along a closed operating path defined by a driving device (10) to withdraw periodically therefrom a sheet article and to stack each sheet article to form corresponding packs of sheet articles; said driving device (10) having: a frame (10 a); motor means (50) having an electronically controllable rotation speed, said motor means providing rotation mechanical power for driving said comb-like folding means (2); mechanical transmission means (13), mounted on said frame (10 a), and being connected to said comb-like folding means (2) and to a transmission shaft (14), connected in turn to said motor means (50), said mechanical transmission means using said rotation mechanical power for providing controlled oscillations of said folding means (2) to drive said folding arms (3) along said closed operating path; a programmable control unit, connected to said motor means (50) and provided with a processing program, for regulating the rotation speed of said motor means (50) in relation to a position assumed by said folding arms (3) traveling along the closed operating path.
 13. The device as claimed in claim 12, wherein said motor means (50) comprise a single electric motor with a controllable speed, operable independently from the driving of said interfolding machine.
 14. The device as claimed in claim 13, wherein said single electric motor is a brushless type motor.
 15. The device as claimed in claim 13, wherein said single electric motor is an electric asynchronous motor or an electric stepping motor.
 16. The device as claimed in claim 12, wherein said motor means (50) comprise: main motor means (51), operable at a predetermined speed, for supplying at least a part of the rotational mechanical power necessary for driving said comb-like folding means (2); supplementary motor means (55), operable at a controllable rotation speed, for cooperating with said main motor means in driving said comb-like folding means; differential transmission means (20), mounted on said frame (10 a), and being connected mechanically to said main motor means (51), to said supplementary motor means (55) and to said mechanical transmission means (13), for receiving at an intake thereof, rotational mechanical power generated respectively by said main motor means and said supplementary motor means, and for supplying a corresponding rotational mechanical power to said mechanical transmission means (13), with a speed defined by a combination of the speeds of said main motor means and said supplementary motor means; said programmable control unit adjusting the rotation speed induced by said supplementary motor means in relation to the position assumed by said folding arms (3) in said closed operating path.
 17. The device as claimed in claim 16, wherein said differential transmission means (20) comprise an epicycloidal type mechanical differential, provided with a first power intake (21), connected to said main motor means (51), with a second axial power intake (22), connected to said supplementary motor means (55), and with a power take-off (23), arranged axially with said second power intake (22), said power take-off (23) connected to said mechanical transmission means (13), a rotation speed of said power take-off being defined by a combination of the rotation speed induced by said main motor means (51) in the first power intake (21) and the speed induced by said supplementary motor means (55) in the second power intake (22).
 18. The device as claimed in claim 16, wherein said supplementary motor means (55) includes a brushless type position controllable motor.
 19. The device as claimed in claim 17, wherein said supplementary motor means (55) includes a brushless type position controllable motor.
 20. The device as claimed in claim 16, wherein said supplementary motor means (55) includes an asynchronous motor or an electric stepping motor.
 21. The device as claimed in claim 17, wherein said supplementary motor means (55) includes an asynchronous motor or an electric stepping motor.
 22. The device as claimed in claim 16, wherein said main motor means (51) are connected to said first power intake (21) by a mechanical transmission assembly (31) having a transmission belt (35), acting on said first power intake (21) of the differential transmission means (20).
 23. The device as claimed in claim 17, wherein said main motor means (51) are connected to said first power intake (21) by a mechanical transmission assembly (31) having a transmission belt (35), acting on the first power intake (21) of the epicycloidal type differential transmission means.
 24. The device as claimed in claim 16, wherein said supplementary motor means (55) include a first supplementary brushless motor (55 a) and a second supplementary brushless motor (55 b); said differential transmission means (20) comprising a first mechanical differential (20 a) and a second mechanical differential (20 b), each mechanical differential being of the epicycloidal type; the first mechanical differential (20 a) and the second mechanical differential (20 b) being oppositely mounted and axially aligned, each of the first and second mechanical differentials having a respective first power intake (21 a, 21 b) connected to said main motor means (51), and each having a respective second power intake (22 a, 22 b) connected to the respective first and second supplementary motors (55 a, 55 b), each of said first and second mechanical differentials (20 a, 20 b) having a respective power takeoff (23 a, 23 b), arranged axially with respect to each other and said second power intake, said first and second power take-offs being axially aligned and being connected to opposite sides of said mechanical transmission means (13), rotation speeds of said power take-offs being defined by a combination of a rotation speed induced by said main motor means at the respective first power intakes and a speed induced by each of said first and second supplementary motor means at the respective second power intakes, the rotation speed of each of said first and second supplementary motors being synchronized by a control unit of said interfolding machine.
 25. The device as claimed in claim 24, wherein said main motor means (51) are connected to said first power intake (21 a) of said first mechanical differential by a mechanical transmission assembly (31) having a first transmission belt (35 a) that acts on said first power intake (21 a) of said first mechanical differential (20 a), the main motor means (51) being also connected to said first power intake (21 b) of said second mechanical differential (20 b) by the mechanical transmission assembly (31) having a second transmission belt (35 b) that acts on said first power intake (21 b) of said second mechanical differential (20 b). 